netdev - Re: [PATCH net-next v6] page_pool: disable dma mapping support for 32-bit arch with 64-bit DMA

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Date:   Mon, 15 Nov 2021 09:59:50 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Ilias Apalodimas <ilias.apalodimas@...aro.org>
Cc:     Yunsheng Lin <linyunsheng@...wei.com>,
        Guillaume Tucker <guillaume.tucker@...labora.com>,
        davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linuxarm@...neuler.org,
        hawk@...nel.org, akpm@...ux-foundation.org, peterz@...radead.org,
        will@...nel.org, jhubbard@...dia.com, yuzhao@...gle.com,
        mcroce@...rosoft.com, fenghua.yu@...el.com, feng.tang@...el.com,
        jgg@...pe.ca, aarcange@...hat.com, guro@...com,
        "kernelci@...ups.io" <kernelci@...ups.io>
Subject: Re: [PATCH net-next v6] page_pool: disable dma mapping support for
 32-bit arch with 64-bit DMA

This is just popping out of nowhere on lkml, but yes ARM LPAE
uses a 64-bit dma_addr_t, as a 64-bit phys_addr_t implies that.
Same for x86-32 PAE and similar cases on MIPS and probably a few
other architectures.

But what is the actual problem with a 32-bit virtual and 64-bit
pysical/dma address?  That is a pretty common setup and absolutely
needs to be deal with in drivers and inrastructure.